Odd wording you chose, but Earth will no longer be a planet in about 5 billion years from now when Sun enters its red giant phase, gradually increasing its radius to end up engulfing Mercury, Venus, and Earth. Human life, however will have to leave the solar system much sooner than that, as over the course of a star like Sun's life, it will gradually increase in luminosity. Luminosity is energy output, and the more energy Sun outputs, the more heat is dissipated. In about a billion years, Earth will be as hot as Venus is now, leaving it uninhabitable.